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Biomedical subjects

S Hong

Publications and source records attributed to S Hong.

At least 127 records · Page 7Linked to original sources
PubMed1998

Farnesylcysteine methyltransferase activity and Ras protein expression in human stomach tumor tissue.

The processing pathway of G-proteins and Ras family proteins includes the isoprenylation of the cysteine residue, followed by proteolysis of three terminal residues and alpha-carboxyl methyl esterification of the cysteine residue. Farnesylcysteine methyltransferase (FCMT) activity is responsible for the methylation reaction which play a role in the membrane attachment of a variety of cellular proteins. Four kinds of Ras protein (c-Ha-ras, c-N-Ras, c-Ki-Ras, pan-Ras) expression were detected in adenocarcinoma of human tissue by immunohistochemical method, and hematoxylin and eosin staining. The level of Ras protein in human stomach tumor tissues was much higher than in normal and peritumoral regions of the same biopsy samples. The FCMT activities of each cellular fractions were high in mitochondrial fraction followed by microsomal fraction, whole homogenate and cytosolic fraction. The inhibitory effect on FCMT activity on stomach tumor tissue was determined after treatment with 0.25 microM of S-adenosyl-L-homocysteine. S-adenosyl-L-homocysteine inhibited FCMT activity from 11.2% to 30.5%. These results suggested that FCMT might be involved in Ras proteins activity.

Adenocarcinoma↗
PubMed1998

Structural modification of an orally active thrombin inhibitor, LB30057: replacement of the D-pocket-binding naphthyl moiety.

An amidrazonophenylalanine derivative LB30057 (2) was identified as a potent (Ki = 0.38 nM), selective, and orally active thrombin inhibitor. As a continuation of studies into benzamidrazone-based thrombin inhibitors, we have structurally modified compound 2 by replacing the naphthyl group with a variety of hydrophobic moieties. This study led to discovery of several compounds with significantly enhanced potency in thrombin inhibition without sacrificing selectivity against trypsin and oral absorption. The highest activity was obtained with compound 23 (Ki = 0.045 nM).

Administration, Oral↗
PubMed1998

Nuclear-gene mutations suppress a defect in the expression of the chloroplast-encoded large subunit of ribulose-1,5-bisphosphate Carboxylase/Oxygenase

The green alga Chlamydomonas reinhardtii mutant 76-5EN lacks photosynthesis because of a nuclear-gene mutation that specifically inhibits expression of the chloroplast gene encoding the large subunit of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco; EC 4.1.1.39). Photosynthesis-competent revertants were selected from mutant 76-5EN to explore the possibility of increasing Rubisco expression. Genetic analysis of 10 revertants revealed that most arose from suppressor mutations in nuclear genes distinct from the original 76-5EN mutant gene. The revertant strains have regained various levels of Rubisco holoenzyme, but none of the suppressor mutations increased Rubisco expression above the wild-type level in either the presence or absence of the 76-5EN mutation. One suppressor mutation, S107-4B, caused a temperature-conditional, photosynthesis-deficient phenotype in the absence of the original 76-5EN mutation. The S107-4B strain was unable to grow photosynthetically at 35 degreesC, but it expressed a substantial level of Rubisco holoenzyme. Whereas the 76-5EN gene encodes a nuclear factor that appears to be required for the transcription of the Rubisco large-subunit gene, the S107-4B nuclear gene may be required for the expression of other chloroplast genes.

Journal Article↗
PubMed1998

Effects of Huangdan capsule on plasma cGMP and ANP in rats with chronic renal failure.

The model of chronic renal failure (CRF) was made in 5/6 nephrectomized rats and Huangdan capsule was used to treat these rats. The levels of cyclic guanosine monophosphate (cGMP) and atrial natriuretic peptide (ANP) in plasma were examined. The results showed that Huangdan capsule could postpone the increase in the levels of cGMP and ANP, suggesting that by regulating the water and sodium metabolism, Huangdan capsule could ameliorate the glomerular filtration rate, and that Huangdan capsule could lower the levels of cGMP and ANP in plasma via body regulation.

Animals↗
PubMed1998

[Specific IgG and specific IgG subclass in allergic rhinitis].

Using enzyme-linked immunosorbent assay, we detected the levels of total IgE, caddis fly specific IgE and caddis fly specific IgG subclass in 60 patients with caddis fly allergic rhinitis. The results showed that the levels of SIgE (30.60 +/- 0.78) of patients were significantly higher than that of the controls (P < 0.001). Same results were received in the levels of specific IgG2 and IgG4. The differences of specific IgE and specific IgG4 between the groups before treatment and after treatment were also significant (Specific IgE before treatment: 30.60 +/- 0.78, after treatment: 1.58 +/- 0.44, P < 0.001; specific IgG4 before treatment: 383.31 +/- 96.48, after treatment: 233.68 +/- 80.94, P < 0.001). We conclude that specific IgG subclass has obviously etiologic specificity and sensitivity.

Adolescent↗
PubMed1998

[Study on the experimental infection of hepatitis G virus in rhesus monkey].

In order to study the experimental infection of HGV in rhesus monkey, the monkeys were infected using the plasma from a donor with HGV RNA positive. The second generation monkeys were infected with the sera of the first generation monkeys infected after 6 weeks, and also the third generation monkeys were infected with the sera of the second generation monkeys. HGV RNA were detected by RT-nPCR. The results showed that in sera of infected monkeys HGV RNA were positive after 1 week of inoculation, and were consecutively positive for up to 28 weeks at longest. The level of ALT raised a little in monkey No. 1 and higher than 100 U/L in No. 5. The liver biopsy showed viral hepatitis--like histological changes. Comparing the sequence of HGV 5'LTR from sera of the infected monkeys and the blood donor, the homogeneity, to strain HGU44402 was 98.33% and 95.83% to strain HGU36380 was 92.50% and 89.17%, respectively. The results suggested that the rhesus monkey is sensitive to HGV and is suitable for establishment of an animal model.

Animals↗
PubMed1997

Kinetics of Permeate Flux Decline in Crossflow Membrane Filtration of Colloidal Suspensions.

A series of well-controlled membrane filtration experiments are performed to systematically investigate the dynamic behavior of permeate flux in crossflow membrane filtration of colloidal suspensions. Results are analyzed by a transient permeate flux model which includes an approximate closed-form analytical expression for the change of permeate flux with time. The model is based on a simplified particle mass balance for the early stages of crossflow filtration before a steady-state flux is attained, and Happel's cell model for the hydraulic resistance of the formed particle cake layer. The filtration experiments demonstrate that permeate flux declines faster with increasing feed particle concentration and transmembrane pressure and with a decrease in the particle size of the suspension. It is also shown that crossflow velocity (shear rate) has no effect on permeate flux at the transient stages of crossflow filtration. Pressure relaxation experiments indicate that the particle cake layer is reversible, implying no irreversible deposition (attachment) of particles onto the membrane surface or the accumulated (retained) particles. The experimental results are shown to be in very good agreement with the theoretical predictions, thus verifying the validity of the model for the transient permeate flux in crossflow filtration and the underlying assumptions in the derivation of the model. Copyright 1997 Academic Press.

Journal Article↗
PubMed1997

Phorbol myristate acetate-dependent association of protein kinase C alpha with phospholipase D1 in intact cells.

A phospholipase D1 (PLD1) was purified from rat brain by the use of antibody-coupled protein A Sepharose. We found that protein kinase C alp (PKCalpha) stimulated PLD1 activity in the presence of phorbol myristate acetate (PMA). PMA-dependent association of PKCalpha with PLD1 was verified in NIH-3T3 fibroblast cells, and COS7 cells transiently expressing PLD1 as well as in vitro suggesting that the activation of PLD1 resulted from direct association of PKCalpha with PLD1.

3T3 Cells↗
PubMed1997

Complementing substitutions at the bottom of the barrel influence catalysis and stability of ribulose-bisphosphate carboxylase/oxygenase.

The temperature-conditional photosynthesis-deficient mutant 68-4PP of Chlamydomonas reinhardtii results from a Leu-290 to Phe substitution in the chloroplast-encoded large subunit of ribulose-1, 5-bisphosphate carboxylase/oxygenase (EC 4.1.1.39). Although this substitution occurs relatively far from the active site, the mutant enzyme has a reduced ratio of carboxylation to oxygenation in addition to reduced thermal stability in vivo and in vitro. In an attempt to understand the role of this region in catalysis, photosynthesis-competent revertants were selected. Two revertants, named R96-4C and R96-8E, were found to arise from second-site mutations that cause V262L and A222T substitutions, respectively. These intragenic suppressor mutations increase the CO2/O2 specificity and carboxylation Vmax back to wild-type values. Based on the crystal structure of the spinach holoenzyme, Leu-290 is not in van der Waals contact with either Val-262 or Ala-222. However, all three residues are located at the bottom of the alpha/beta-barrel active site and may interact with residues of the nuclear encoded small subunits. It appears that amino acid residues at the interface of large and small subunits can influence both stability and catalysis.

Animals↗
PubMed1997

Roles of transmembrane prolines and proline-induced kinks of the lutropin/choriogonadotropin receptor.

The lutropin/choriogonadotropin receptor is a seven-helix transmembrane (TM) receptor. A unique feature of TM helices is the content of Pro, which generally is absent in alpha helices of globular proteins. Because Pro disrupts helices and introduces a approximately 26 degrees kink, it has been speculated that Pro plays a crucial role in the structure of TM helices, exoloops, and cytoloops of TM receptors. To examine the roles of the five TM Pros of the lutropin/choriogonadotropin receptor, these residues were individually substituted. Mutant receptors were examined for surface expression, hormone binding, and cAMP induction. Surface expression was monitored after introducing the flag epitope into the receptors. Flag epitopes slightly affected cAMP induction but not hormone binding or surface expression of receptors as monitored by immunofluorescence microscopy and 125I-anti-flag antibody. The results indicate that Pro479 in TM 4 and Pro598 in TM 7 play important yet contrasting roles. Pro479 is crucial for hormone binding at the cell surface but not after solubilization of the receptor. This is more likely due to the Pro side chain than the Pro-induced kink. Pro598 is important for surface expression. The kinks of Pro463 of TM 4, Pro562 of TM 6, or Pro591 of TM 7 are not important because the substitution of Phe for these residues did not significantly impact surface expression, hormone binding, and cAMP induction.

Amino Acid Sequence↗
PubMed1997

Reactions of isocytochrome c2 in the photosynthetic electron transfer chain of Rhodobacter sphaeroides.

Rhodobacter sphaeroides strains lacking cytochrome c2 (cyt c2), the normal electron donor to P870+ in light-oxidized reaction center (RC) complexes, are unable to grow photosynthetically. However, spd mutations that suppress the photosynthetic deficiency of cyt c2 mutants elevate levels of the cyt c2 isoform, isocyt c2. We monitored photosynthetic electron transfer in whole cells, in chromatophores, and with purified components to ascertain if and how isocyt c2 reduced light-oxidized RC complexes. These studies revealed that several fundamental aspects of photosynthetic electron transfer were similar in strains that use isocyt c2 and wild-type cells. For example, P870+ reduction accompanied cytochrome c oxidation. In addition, photosynthetic electron transfer was blocked by the well-known cyt bc1 complex inhibitors antimycin and myxothiazol. However, even at the increased isocyt c2 levels present in these strains (approximately 40% that of cyt c2 in wild-type cells), there was little, if any, of the rapid (< 5 microns) electron transfer to P870+ that is characteristic of cytochromes bound to RC complexes at the time of the light flash. Thus, it appears that isocyt c2 function limits the in vivo rate of P870+ reduction. Indeed, at low ionic strength in vitro, the apparent affinity of isocyt c2 for RC complexes (KD approximately 40 microM) is significantly lower than that of cyt c2 (KD approximately 1.0 microM). This reduced affinity does not appear to result from an altered mode of RC binding by isocyt c2 since electrostatic interactions make similar overall contributions to the binding of both cyt c2 and isocyt c2 to this membrane-bound redox partner. Thus, sequence, structural, or local conformational differences between cyt c2 and isocyt c2 significantly alter their apparent affinities for this physiologically relevant redox partner.

Cytochrome c Group↗
PubMed1997

Anti-lipid peroxidization effect of huangdan on chronic renal failure in rats.

The activity of superoxide dismutase (SOD) in renal cortex and erythrocytes, the level of lipid peroxidant (LPO) in plasma, renal function and morphology of leftover kidney were examined in rats. The results showed that Huangdan capsule could slow down the increase of BUN and Scr, promote the SOD activity in renal cortex and erythrocytes, reduce the level of LPO in plasma and delay the renal pathological changes in 5/6 nephrectomized rats. The mechanism of Huangdan capsule's antiperoxidant effect, its effect on the renal pathological changes and relationship between the two effects were also discussed.

Animals↗
PubMed1997

One-week therapy with twice-daily butenafine 1% cream versus vehicle in the treatment of tinea pedis: a multicenter, double-blind trial.

BACKGROUND: Butenafine hydrochloride, a benzylamine derivative with potent antifungal activity, has been used in Japan to treat superficial fungal diseases. OBJECTIVE: We evaluated the safety and efficacy of twice-daily butenafine versus its vehicle in the treatment of interdigital tinea pedis in a multicenter, randomized, double-blind, parallel-group trial. METHODS: A total of 402 patients with interdigital tinea pedis and a positive potassium hydroxide examination were enrolled. Of the 271 patients who had culture-confirmed tinea pedis and were assessed for efficacy, 132 applied butenafine and 139 applied vehicle twice daily for 1 week. Patients were assessed for mycologic cure, effective treatment, overall cure, and mycologic/clinical cure. RESULTS: The rates of all four end points were significantly higher with butenafine than with vehicle 5 weeks after treatment ended. Rates of mycologic cure and effective treatment with butenafine were significantly higher than with vehicle at cessation of treatment. Adverse events to treatment occurred in less than 1% of patients treated with butenafine and 2% of patients who applied vehicle. CONCLUSION: Butenafine applied twice daily for 1 week is highly effective in treating interdigital tinea pedis.

Administration, Topical↗
PubMed1997

Introduction of the glutamate receptor subunit 1 into motor neurons in vitro and in vivo using a recombinant herpes simplex virus.

We developed and characterized a recombinant herpes simplex virus vector and used it to introduce the complementary DNA encoding glutamate receptor subunit 1 flip into postmitotic motor neurons. Infection of purified motor neurons in vitro with this vector resulted in selective, high-level expression of glutamate receptor subunit 1 immunoreactivity in nearly 100% of the neurons. Patch-clamp experiments demonstrated that the protein product of the glutamate receptor subunit 1 flip transgene assembles into functional alpha-amino-3-hydroxy-5-methyl-4-isoxazolepropionate (AMPA) receptor channels. Herpes simplex virus-glutamate receptor subunit 1 flip was introduced into spinal cord cells by direct injection into the ventral horn and selectively into motor neurons by sciatic nerve injection. High levels of expression were sustained for at least one week and were accompanied by changes in the ionic permeability of AMPA receptors in transgene-expressing neurons. Throughout the first week of infection, there was little evidence for toxicity. Herpes simplex virus provides a versatile tool for manipulating the glutamate receptor phenotype of postmitotic neurons and will permit study of the role of individual glutamate receptor subunits in neuronal physiology and pathophysiology.

Animals↗
PubMed1997

CD1d1 mutant mice are deficient in natural T cells that promptly produce IL-4.

Murine CD1 has been implicated in the development and function of an unusual subset of T cells, termed natural T (NT) cells, that coexpress the T cell receptor (TCR) and the natural killer cell receptor NK1.1. Activated NT cells promptly produce large amounts of IL-4, suggesting that these cells can influence the differentiation of CD4+ effector T cell subsets. We have generated mice that carry a mutant CD1d1 gene. NT cell numbers in the thymus, spleen, and liver of these mice were dramatically reduced. Activated splenocytes from mutant mice did not produce IL-4, whereas similarly treated wild-type splenocytes secreted large amounts of this cytokine. These results demonstrate a critical role for CD1 in the positive selection and function of NT cells.

Animals↗
PubMed1997

[Alkaloids in the seeds of Zyziphs jujuba Mill].

Two alkaloids were isolated from the seeds of Zyziphs jujuba and identified on the basis of spectral data to be lysicamine and juzirine. These two alkaloids were obtained from the genus for the first time.

Alkaloids↗
PubMed1997

[The establishment of antigen sandwiched ELISA for detection of total antibodies to hepatitis C virus].

An antigen sandwiched ELISA for detection of the total antibodies to HCV was established using genetically engineered proteins and synthesized peptides located in the structural and nonstructural regions of HCV genomes as coated antigens and were labeled by horseradish peroxidase, respectively. A comparison of antigen sandwiched ELISA with indirect ELISA showed that the sensitivity of sandwiched system (1:128) was little higher than that of indirect ELISA (1:64), the specificities of both systems were all 100%. This reagent may detect all classes of antibody to HCV in serum, mainly IgG and IgM and is a new diagnostic reagent for detection and early diagnosis of HCV infection.

Enzyme-Linked Immunosorbent Assay↗